Note:

Since it merged from end, so 

1. tmp1, tmp2 = INT_MIN

2. tmp1 > tmp2

1 class Solution { 2 public: 3     void merge(int A[], int m, int B[], int n) { 4         int total = m+n-1, indexA = m-1, indexB = n-1; 5         while (indexA >= 0 || indexB >= 0) { 6             int tmp1 = INT_MIN, tmp2 = INT_MIN; 7             if (indexA >= 0) { 8                 tmp1 = A[indexA]; 9             }10             if (indexB >= 0) {11                 tmp2 = B[indexB];12             }13             if (tmp1 > tmp2) {14                 A[total--] = A[indexA--];15             } else {16                 A[total--] = B[indexB--];17             }18         }19     }20 };